1. Field of the Invention
The present invention relates to a liquid storage container containing various kinds of liquid such as ink therein.
2. Description of the Related Art
In a recording apparatus for recording images on a recording medium using a recording head by applying liquid, such as ink, on the recording medium, a liquid storage container is provided for containing ink for supplying the ink to the recording head. In order to stably supply the liquid and prevent the liquid leakage, a predetermined negative pressure is generally applied to the liquid contained in such a liquid storage container.
Among configurations of such liquid storage containers, one has been in the form of the container in which a liquid absorbing body is provided for imparting the negative pressure using the power of the absorbing body for holding liquid. Other containers generating the negative pressure without using such an absorbing body include one using a spring as a negative pressure generating mechanism. This closed container has a casing (fixed member) forming part of the container with a flexible member attached thereto, which is deformable in a compression direction along with the outside delivery of ink from the container. Then, the negative pressure is generated in the container by urging the flexible member with a spring in a direction expanding the inner part of the container. Such a spring includes a semi-elliptic leaf spring disclosed in U.S. Pat. No. 5,754,207 and a coil spring in U.S. Pat. No. 6,250,751. As disclosed in Japanese Patent Laid-Open No. H06-183023, there is also a spring contained in a bag-like flexible member as a negative pressure generating mechanism.
In the liquid storage container that generates the negative pressure by the urging of the flexible member with a spring member so as to expand the interior part of the container in such a manner, a protection member, such as a lid member, is provided for protecting the flexible member against external pressure and impact. Such a protection member protects the liquid storage container from the impact and the static load applied by the dropping of the container during handling and shipping. When the deformation of components of the liquid storage container due to the external pressure is transmitted to the flexible member, rapid changes in pressure and the negative pressure cancellation are occurred in the container, leading to the ink leakage. The protection member prevents such ink leakage.
In a liquid storage container made of resins, the deformation of the resin protection member due to the external pressure is difficult to be avoided. When an external pressure is applied to a rectangular parallelepiped liquid storage container, the maximum superficial area part is deformed to the utmost. Hence, the maximum deformation of the flexible member is designed so that the flexible member does not touch the lid member when the flexible member deforms to the utmost in a direction expanding the interior part of the container. The limitation of the maximum deformation of the flexible member substantially reduces the ink storage amount.
In order to prevent the deformation of the protection member, the thickness of the resin forming the member may be increased, or the protection member may be made of a material with a higher rigidity than that of the resin such as a metal.
However, when the thickness of the maximum superficial area part of the container is increased, the ink storage amount is reduced. Use of the high rigid material, such as a metal, also increases product cost.
FIGS. 12A to 13C show configurations of liquid storage containers in which the shape of the flexible member is specified in view of the deformation of the protection member for suppressing the reduction in storage amount. A casing member 1 and a flexible member 4 adhered on the internal periphery of the casing member 1 form a storage space for a liquid 7 such as ink. On the internal surface of the flexible member 4, a plane member 3 is located, and on the opening of the casing member 1, a lid member 5 is attached for protecting the flexible member 4 as a protection member. A spring member 2 provided within the storage space for the liquid 7 urges the flexible member 4 with the plane member 3 therebetween upwardly in FIGS. 13A to 13C, i.e., in a direction expanding the storage space. Thereby, a negative pressure is applied to the liquid 7. FIG. 13B shows the state when the lid member 5 is deformed to the utmost due to an external force. As shown in FIG. 12A, the plane member 3 is provided with a recess 11 formed thereon with approximately the same shape as that of the lid member 5 deformed to the utmost. The relationship between the recess and the liquid storage amount is shown in FIGS. 13A to 13C. The flexible member 4 is always controlled to have substantially the same shape as that of the lid member 5 deformed to the utmost, so that the portion of the flexible member 4 corresponding to that of the plane member 3 is concave.
The plane member 3 is made of a metallic plate or a comparatively thick resin plate (at least 1 to 2 mm in thickness), which are not deformed by low pressure, for transmitting a force generated by the spring member 2. Hence, the downward protruding portion of the recess 11 of the plane member 3, which is formed in approximately the same shape as that of the lid member 5 deformed to the utmost, comes in contact with the internal bottom surface of the casing member 1 when the liquid 7 is used up, as shown in FIG. 13C. As a result, the deformation of the plane member 3 toward the casing member 1 is inhibited. If the flexible member 4 is further deformed from the state of FIG. 13C, the distance between the flexible member 4 and the casing member 1 is further reduced, so that the negative pressure in the liquid storage space is rapidly increased. When the liquid is ink, the ink cannot be supplied to a recording head from an ink supply port 6 at that time. Furthermore, when part of the flexible member 4 comes in contact with the casing member 1, the ink flow to the ink supply port 6 is blocked off in this state, leading to residual ink in the storage space.